1. Field of the Invention
The invention relates to a syringe and more particularly to a syringe for easily metering predetermined volumes of fluid therefrom.
2. Description of the Related Art
In many situations, it is necessary to either fill a syringe with a precise volume of fluid or discharge a precise volume of fluid from the syringe. Other situations require that precise volumes of fluid be incrementally discharged over a period of time.
In order to control the volumetric intake to and discharge from a syringe, a syringe tube typically has a visual scale calibrated in volumetric units. Therefore, a plunger inside the syringe tube is translated along the scale a distance corresponding to the desired fluid volume.
While such a scale is functional, circumstances may arise which make the scale difficult to read. For example, the fluid may have a color which does not contrast with the color of the scale. Further, there may be distortions in the scale from manufacturing. Variations in the eyesight of the person using the syringe may also make the scale difficult to read and use. Photosensitive fluids require an opaque syringe tube which makes it impossible to use a syringe tube scale. Finally, the discharge of successive precise volumes of fluid requires precise control of the plunger relative to the scale so that too much or too little fluid is not metered through the syringe. Precise control becomes more difficult with smaller dosages which require smaller plunger movements.